content/apt/examples/maven-3-lifecycle-extensions.apt.vm

  ---
  Example: Maven 3 lifecycle extension
  ---
  Olivier Lamy
  ---
  2012-03-07
  ---

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Example: Using Maven 3 lifecycle extension

* Lifecyle Participation

  You can extend multiple classes depending on your needs:

  * {{{/ref/current/maven-core/apidocs/index.html?org/apache/maven/execution/AbstractExecutionListener.html}<<<org.apache.maven.execution.AbstractExecutionListener>>>}},

  * {{{/ref/current/maven-core/apidocs/index.html?org/apache/maven/AbstractMavenLifecycleParticipant.html}<<<org.apache.maven.AbstractMavenLifecycleParticipant>>>}},

  * {{{/ref/current/maven-core/apidocs/index.html?org/apache/maven/eventspy/AbstractEventSpy.html}<<<org.apache.maven.eventspy.AbstractEventSpy>>>}},

  []

* Build your extension

  Create a Maven project with a dependency on <<<org.apache.maven:maven-core:${currentStableVersion}>>> and other dependencies:

+---+
    <groupId>org.apache.maven.extensions</groupId>
    <artifactId>beer-maven-lifecycle</artifactId>
    <version>1.0-SNAPSHOT</version>

    <dependency>
      <groupId>org.apache.maven</groupId>
      <artifactId>maven-core</artifactId>
      <version>${currentStableVersion}</version>
    </dependency>

    <!-- dependency for plexus annotation -->
    <dependency>
      <groupId>org.codehaus.plexus</groupId>
      <artifactId>plexus-component-annotations</artifactId>
      <version>1.7.1</version>
    </dependency>
+---+

  Create your extension class

+---+
// your extension must be a "Plexus" component so mark it with the annotation
@Component( role = AbstractMavenLifecycleParticipant.class, hint = "beer")
public class BeerMavenLifecycleParticipant extends AbstractMavenLifecycleParticipant
{

    @Override
    public void afterSessionStart( MavenSession session )
        throws MavenExecutionException
    {
      // start the beer machine
    }


    @Override
    public void afterProjectsRead( MavenSession session )
        throws MavenExecutionException
    {
      // ask a beer to the machine
    }

}
+---+

  Generate plexus metadata during the build of your extension jar:

+---+
  <build>
    ...
    <plugins>
      ...
      <plugin>
        <groupId>org.codehaus.plexus</groupId>
        <artifactId>plexus-component-metadata</artifactId>
        <version>1.7.1</version>
        <executions>
          <execution>
            <goals>
              <goal>generate-metadata</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
      ...
    </plugins>
    ...
  </build>
+---+

* Use your extension in your build(s)

  You have 3 ways to use your extension within your builds:

  * add your extension jar in <<<$\{maven.home\}/lib/ext>>>,

  * add it as a build extension in your pom,

  * (since Maven 3.3.1) configure your extension in {{{/ref/current/maven-embedder/core-extensions.html}<<<.mvn/extensions.xml>>>}}.

  []

  <<NOTE>>: if you use the build extension mechanism, the method <<<afterSessionStart>>> <<won't be called>> since the extension
  is loaded later in the build

  To use a build extension in your project, declare it in your pom as:

+---+
   <build>
     ...
     <extensions>
       ...
       <extension>
         <groupId>org.apache.maven.extensions</groupId>
         <artifactId>beer-maven-lifecycle</artifactId>
         <version>1.0-SNAPSHOT</version>
       </extension>
       ...
     </extensions>
    ...
   </build>
+---+